Modern integrated circuits (ICs), such as non-volatile memories, include thousands of components. Due to variations in semiconductor processing, not all of the components in the IC are fabricated to desired specifications. When components of the IC are not fabricated as desired, the IC may not operate properly.
It is therefore desirable to evaluate the components during or after IC fabrication. One method of testing a component of an IC is performed by extracting an internal signal in the IC, corresponding to the component, and externally comparing the potential, or voltage, of the internal signal with a comparison voltage. If the comparison demonstrates that the potential of the internal signal is excessively larger or smaller than the comparison voltage, the corresponding IC component is shown to be fabricated improperly.
The internal signals of memory ICs are typically extracted by applying a micro-probe to the IC component or routing the internal signal through a multiplexer to a common probe point. The micro-probing technique requires the use of complex computer micro-probe cards. Also, internal signals having negative or relatively large potentials, such as required in non-volatile memories, are extracted with difficulty with micro-probe cards. Relatively large potentials are potentials that exceed supply voltages provided to the non-volatile memory, such as the programming voltage required in non-volatile memories. These relatively large voltages are typically generated with internal voltage pumps.
The micro-probe cards cannot typically be employed to characterize internal signals of mounted or packaged IC memories. Thus, after an IC memory is packaged, the multiplexing technique is typically used to read out internal voltages, which requires complex multiplexing circuitry in the memory IC. The complicated multiplexing circuitry complicates the memory design and testing process, particularly for internal signals having negative potentials. In fact, in many cases even with modem pico-probes, negative voltages cannot be extracted from the memory IC. Therefore, there is a need for a technique to more effectively analyze internal signals of an IC, such as a non-volatile memory, particularly internal signals having negative or large potentials. Furthermore, there is a need for a technique to more effectively analyze internal signals of a mounted or packaged IC, such as a non-volatile memory.